<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
    .box1 {
        border: 1px solid red;
        background-color: yellow;
    }
    
    .empty{
        clear: both;
    }
    
    .box2 {
        width: 50px;
        height: 50px;
        float: left;
        background-color: orange;
    }
    
    p {
        float: right;
    }
    </style>
</head>

<body>
    <div class="box1 clear">
        <div class="box2">
            box2
        </div>
        
        <p>
            lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦 lallalalalalal啦啦啦
        </p>
        <br class="empty" />
    </div>
</body>

</html>